Add Current Phase Campaign Key to Subscriptions Export

🔍 Problem Statement

As a Pelcro admin exporting subscription data, the current campaign_key column reflects the key set at subscription creation, not the campaign key of the current active phase, which results in inaccurate campaign attribution for multi-phase or renewed subscriptions.

💡 User Story

As a Pelcro admin, I want the subscriptions export to include a current_phase_campaign_key column, so that I can accurately attribute each subscription to the campaign that drove its current active phase.

🎯 Definition of Done (DoD)

✔ Given a subscription with multiple phases, each linked to a different campaign key, when the subscriptions export is generated, then a new current_phase_campaign_key column reflects the campaign key of the currently active phase — distinct from the original campaign_key column.

✔ Given a subscription with no campaign key on the current phase, when the subscriptions export is generated, then the current_phase_campaign_key column is empty (not null-errored).

✔ This change will impact API and Data, specifically the subscriptions export endpoint and CSV generation logic.

✔ This solution will include the following limitations: current_phase_campaign_key is read-only in the export and does not replace the existing campaign_key column; phase history is out of scope.